1. Field of the Invention
The present invention relates to wireless communication and, more specifically, to a method and apparatus for transmitting uplink control information in a wireless communication system.
2. Related Art
Effective transmission/reception methods and utilizations have been proposed for a broadband wireless communication system to maximize efficiency of radio resources. An orthogonal frequency division multiplexing (OFDM) system capable of reducing inter-symbol interference (ISI) with a low complexity is taken into consideration as one of next generation wireless communication systems. In the OFDM, a serially input data symbol is converted into N parallel data symbols, and is then transmitted by being carried on each of separated N subcarriers. The subcarriers maintain orthogonality in a frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, and an interval of a transmitted symbol is increased, thereby minimizing inter-symbol interference.
When a system uses the OFDM as a modulation scheme, orthogonal frequency division multiple access (OFDMA) is a multiple access scheme in which multiple access is achieved by independently providing some of available subcarriers to a plurality of users. In the OFDMA, frequency resources (i.e., subcarriers) are provided to the respective users, and the respective frequency resources do not overlap with one another in general since they are independently provided to the plurality of users. Consequently, the frequency resources are allocated to the respective users in a mutually exclusive manner. In an OFDMA system, frequency diversity for multiple users can be obtained by using frequency selective scheduling, and subcarriers can be allocated variously according to a permutation rule for the subcarriers. In addition, a spatial multiplexing scheme using multiple antennas can be used to increase efficiency of a spatial domain.
Uplink control information (UCI) can be transmitted through a physical uplink control channel (PUCCH). The UCI can include various types of information such as a scheduling request (SR), an acknowledgement/non-acknowledgement (ACK/NACK) signal for hybrid automatic repeat request (HARQ), a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), etc. The PUCCH carries various types of control information according to a format.
Uplink control information may be subject to channel coding and transmitted. Any one of various types of coding methods, such as simple repetition, simplex coding, RM coding, punctured RM coding, tail-biting convolution coding (TBCC), low density parity check (LDPC) coding, and turbo coding, may be used as the channel coding method. Each of the channel coding methods have advantages and disadvantages depending on channel environments or systems, and some of the channel coding methods may have different channel coding performance depending on the length of information. Furthermore, in some of the channel coding methods, channel coding may not be performed on information having a length of a constraint length or less.
Accordingly, there is a need for a method of efficiently performing channel coding on information having a length of a constraint length or less.